Recently, calcium phosphate based ceramics have increased their use as artificial teeth implants, artificial bones, etc., since they have an excellent affinity to the living body.
In the application of calcium phosphate ceramics to a living body as teeth implants, artificial bones, and the like, it is known that the affinity is much improved by increasing surface porosity and thus promoting the circulation of the humor.
Accordingly, various production processes for porous calcium phosphate ceramics are suggested. Usually employed processes are as follows:
(1) A slurry of calcium phosphate based compound is foamed by adding a foaming agent, molded to a predetermined shape, dried, and fired (as described in "Sintered hydroxyapatite as a bioceramics", Philips tech. Rev., vol. 37, pp 234-236, 1977, No. 9/10);
(2) A powder of calcium phosphate based compound is mixed with a pyrolytic organic substance, molded, pre-calcined, and fired (as described in JP-A-62-22632) (The term "JP-A" as used herein means an "unexamined published Japanese patent application").
However, the aforesaid processes tend to be complicated since they include foaming with foaming agents or mixing with pyrolytic organic matter. Moreover, the strengths of the porous ceramics are considerably low as compared with non-porous ceramics, since they are wholly composed of porous material from the inside to the surface.